1. Field of the Invention
This invention relates to a zoom lens, and in particular, to a zoom lens including three lens units which is small in size and low in cost and has a wide angle of view, suitable for a compact camera.
2. Description of Related Art
A zoom lens including two lens units which is simple in arrangement has been often used as a zoom lens for compact cameras. In the zoom lens for compact cameras, however, demands for a compact design and a high variable magnification function have been increased. In particular, for the variable magnification function, a demand for a wide angle of view at a short focal length has been enhanced. Therefore, in the zoom lens including two lens units which is simple in arrangement, there is a limit to holding of favorable balance of aberration ranging from the short focal length to the long focal length. Thus, a zoom lens including three lens units has come to be chiefly used.
Furthermore, a lens system for compact cameras, in contrast with that for single lens reflex cameras, has the advantages that there is little need to increase a back focal distance and the overall length can be reduced. Consequently, a telephoto-type system in which the last lens unit has a negative characteristic is often used. In particular, in the zoom lens including three lens units, a lens arrangement with positive, positive, and negative powers has widespread use. In addition to satisfying these requirements, there is a further demand for low cost.
Zoom lenses set forth, for example, in Japanese Patent Kokai Nos. Hei 11-119098, Hei 10-90600, and 2000-275524 are proposed as the above conventional zoom lenses.